Improving the control of styrene polymerization at 60 °C using a dialkylated α‐hydrogenated nitroxide

Abstract

A new dialkylated α‐hydrogenated linear nitroxide and the corresponding 1‐phenylethyl alkoxyamine were synthesized in two and three steps, respectively. The alkoxyamine was involved in the polymerization of styrene at 60 °C, and the in situ concentration of nitroxide was monitored by electron spin resonance spectroscopy. The enhanced characteristics of these new alkylated alkoxyamine and nitroxide (k d60 = 1.5 × 10−4 s−1 and k c60 = 5.7 × 104 L mol−1 s−1) yielded a monomer consumption one order of magnitude higher than styrene thermal polymerization. This resulted in well‐defined polystyrenes up to 70,000 g mol−1 and the observation of a control occurring through the establishment of the radical persistent effect, that is, ln([M]0/[M]) = t2/3. Experimentally determined kinetic constants were involved in PREDICI modelings to investigate the influence of temperature and initial alkoxyamine concentration on the kinetics as well as on the livingness and the controlled character of the polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

H‐transfer reaction during decomposition of N‐(2‐methylpropyl)‐ N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐N‐oxyl (SG1)‐based alkoxyamines

“…One of the most effective NMP mediators of many styrenic and acrylic monomers is the N ‐(2‐methylpropyl)‐ N ‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐ N ‐oxyl radical (SG1) 9. Up to date, NMP of alkyl methacrylates, in particular methyl methacrylate (MMA), is very demanding, although a number of attempts using different nitroxides or alkoxyamines have been performed 10–19. The main complication for NMP of MMA is the occurrence of side reactions, namely, the intramolecular β‐proton transfer (IPT, Cope‐type elimination20), intermolecular β‐hydrogen atom transfer (IHAT) reactions (reactions (ii) and (iv), respectively, in Scheme ), irreversible decomposition of dormant species (i.e., through NO bond homolysis),21–23 and decomposition of persistent nitroxyl radicals in the course of NMP.…”

Controlled/living polymerization of methyl methacrylate using new sterically hindered imidazoline nitroxides prepared via intramolecular 1,3-dipolar cycloaddition reaction

“…The conditions were selected according to the Fischer's diagram (see above).The polymerization was performed at 120 °C with monomer to initiator ratio 350 to 1. It should be noted that typically NMP of styrene proceeds at elevated temperatures; however, recently new nitroxide families allowed for considerable decrease in polymerization temperatures …”

Deterministic Approaches for Simulation of Nitroxide-Mediated Radical Polymerization

“…Even though the full MWD is available, many works in which Predici was used reported only the prediction of the MWD averages, such as M n and M w . These works presented an analysis of reaction steps, in comparison with experimental data and understanding of the influence of operating conditions [75][76][77][78][79][80][81][82][83][84]. For instance, Gigmes et al [75] studied the influence of several kinetic parameters and reaction steps on the livingness and controlled character of a generic NMP.…”

“…They studied DC effects, showing that the gel effect was not required to improve the fit of the simulation of polymerizations leading to low molecular weight material. Guillaneuf et al [81] synthesized a new nitroxide, a dialkylated α-hydrogenated linear compound, and the corresponding 1-phenylethyl alkoxyamine, which yielded enhanced polymerization rate in the NMP of styrene. They used a Predici model of the system to study the effect of temperature and alkoxyamine concentration on the kinetics and on the livingness and controlled character of the polymerization.…”